Caracterização produtiva, morfológica e nutricional dos capins Mulato II e Marandu em diferentes alturas de dossel

• Ano de defesa: 2017
• Autor(a) principal: Silva, Lilian Chambó Rondena Pesqueira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Mato Grosso; Brasil; Faculdade de Agronomia e Zootecnia (FAAZ); UFMT CUC - Cuiabá; Programa de Pós-Graduação em Ciência Animal
• Palavras-chave em Português: Adubação; Composição bromatológica; Digestibilidade in vitro; Metano; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA; Chemical composition; Fertilization; In vitro digestibility; Methane
• Link de acesso: http://ri.ufmt.br/handle/1/4366

Three experiments were carried out to evaluate the productive, morphological and nutritional value of Brachiaria hybrid cultivar Mulato II in comparison to Brachiaria brizantha Marandu cultivar, under different canopy heights. The experimental design was completely randomized in a 2x4 factorial scheme: two forages (Mulato II and Marandu) and four pre-cut canopy heights (30, 45, 60 and 75 cm), with six replications. The area of each plot was 20m2 . The first two experiments were similar, being distinct only by the use of fertilization in the first, and absence of this in the second, simulating a system of low adoption of technology. In both, the evaluations were carried out from April 2015 to March 2016, separated by seasons (autumn, winter/spring and summer). In the first experiment, during the autumn, Mulato II showed lower (P<0.05) forage mass (FM), pseudostem and fiber, and higher (P<0.05) foliar leaf/pseudostem, crude protein (CB) and in vitro organic matter digestibility (IVOMD). During winter/spring and summer, there was no distinction (P>0.05) between grasses for FM. Mulato II presented lower (P<0.05) fiber fractions. In both grasses, the increase of the pre-cut canopy height from 30 to 75 cm resulted in smaller (P<0.05) means for leaf blade, foliar leaf/pseudostem ratio, IVOMD, metabolizable energy and total digestive nutrients. In the second experiment, at all periods of the year, the grasses did not reach the proposed heights of 75 cm. The FM among the grasses did not differ (P>0.05) in all periods of the year, except for height of 60 cm in the autumn in which the Mulato II grass showed lower (P<0.05) average than the Marandu grass. During the autumn there was no difference (P>0.05) between the grasses for CP and neutral detergent fiber indigestible (NDFi). In this period, Mulato II presented lower (P<0.05) fiber fraction in neutral detergent fiber corrected for ash and protein (NDFap), acid detergent fiber (ADF) and acid detergent insoluble nitrogen (ADIN). In the winter/spring season, Mulato II grass presented higher (P<0.05) leaf blade and PB fraction, and smaller (P<0.05) fractions of pseudostem, NDFap, ADF, ADIN and NDFi. In summer, higher (P<0.05) CP and lower (P<0.05) ADIN were found in Mulato II grass. In all periods of the year, the increase in pre-cut canopy height from 30 to 75 cm resulted in higher (P<0.05) pseudostem, dead material, fibers, and ADIN and lower (P<0.05) CP. In the third experiment, Multato II presented higher (P<0.05) mean gas production at all incubation times at heights of 45 and 75 cm. In both grasses, at times 6, 12, 24h and in times 48 and 72h only for Marandu grass, there was a linear effect (P<0.05) decreasing for the cumulative production of gases as a function of the heights of the pre-court. The total gas production (GP) was higher (P<0.05) in Mulato II grass with 45 and 60 cm in height, and CH4 (mL g MSi-1), with 75 cm. (P<0.05), the highest (P<0.05) in vitro dry matter digestibility (IVDMD) with 12h incubation, and higher (P<0.05) gas volume of the fast digestion fraction (V1) were obtained with Mulato II grass. In both grasses, the increase of precut canopy height, in general, promoted a linear increase (P<0.05) in V2 and a linear reduction (P<0.05) in IVDMD in CH4 volumes expressed in relation to the digested MS and to the digested neutral detergent fiber (NDFd), and in V1. The volume of CH4 in relation to the total gas produced (mL CH4 total of L-1 gas), the total amount and individual molar ratio of the short chain fatty acids, and the acetate: propionate ratio were not influenced (P>0.05) by the weeds and heights of the pre-cut canopy. In conclusion, Mulato II grass does not present productive advantages in relation to Marandu grass during the year, but has a better canopy structure, even without the use of fertilization. It presents a higher fraction of non-fibrous carbohydrates, is less sensitive to loss of fermentative potential with canopy height, and does not differ from Marandu grass for the production of short chain fatty acids and methane volume. The cutting height or pre-grazing height of 30 cm allows both forage production of better nutritive value, with greater potential for gas production, and both, in this condition, can contribute to the mitigation of methane per unit of product produced.